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  #11  
Old 05-13-2020, 01:14 PM
RobVG RobVG is offline
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Default Added the front fins

They reduced Cal just a bit. Adding an additional 0.1 oz brought it just above 1.0

Adding more weight increase it very slowly.
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  #12  
Old 05-13-2020, 01:26 PM
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100 feet on a no-wind day. That's dicey even with a 3-second delay getting a 'chute out and open before it hits the ground. D12 would be a minimum for safe flight. There also 3 second delay. I would not try a Q-Jet D16-4 until I saw it fly on an Estes D12-3.

Thinking of it as a dual egg lofter makes the numbers sound more plausible to me.

Now that Sixty Acres is open again (I had the north field all to myself on Monday from 11:30 to about 3) you could fly it over there on an E30.
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  #13  
Old 05-13-2020, 02:04 PM
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neil_w neil_w is offline
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Quote:
Originally Posted by RobVG
Haven't yet figured out how to add the forwad fin set . To make it look right they need to be placed on the nose cone.

If you're talking about the forward fins on the current iteration of Starship, be forewarned they will pull the CP forward and you'll need even *more* noseweight.

The way to add them in current version of OR is:
1) Split the nose cone into a cone and a transition, with the break point at the leading edge of the fins.
2) Insert a zero-length body tube between them
3) Mount the nose cone fins to that body tube.
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  #14  
Old 05-14-2020, 02:29 PM
RobVG RobVG is offline
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Quote:
Originally Posted by neil_w

The way to add them in current version of OR is:
1) Split the nose cone into a cone and a transition, with the break point at the leading edge of the fins.
2) Insert a zero-length body tube between them
3) Mount the nose cone fins to that body tube.


I was able to add them another way Neil. Clicking on the body tube allowed me to add a second set of free form fins. They ended up on the rear of the rocket and I was able to reposition them on the nose cone. I'll try your method to gain some more experience with OR.

Thanks!
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  #15  
Old 05-14-2020, 02:50 PM
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Quote:
Originally Posted by RobVG

Haven't yet figured out how to add the forwad fin set . To make it look right they need to be placed on the nose cone.


A good way to add fins to the nose cone, assuming your concern is due to them being mounted on a plastic nose cone, is to first cut fin slots. You want to make them thru-wall so they are well anchored. Have the tabs meet in the center of cone, where they can be glued together. I use a bit of epoxy at the fin-nose cone joint, if filling is needed, and follow up with putty if any additional fill or smoothing is needed.
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  #16  
Old 05-14-2020, 03:11 PM
RobVG RobVG is offline
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Thanks Lee. Slots sound like a good idea.
Don't think I'll be able to get the tabs to meet. It'd be hard to add the weight.

Leaving shortly to get balsa wood. No paint until it flies.

When the time comes, it'll be launched at dawn. Don't want anyone around.
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  #17  
Old 05-15-2020, 12:38 PM
RobVG RobVG is offline
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They didn't have balsa. Gonna give basswood a try.
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  #18  
Old 05-15-2020, 02:19 PM
RobVG RobVG is offline
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Well dang lol. just opened OR again and the weight "did" include engines. 10.7 oz.
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  #19  
Old 05-18-2020, 01:49 PM
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luke strawwalker luke strawwalker is offline
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If nose fins are messing up your CG/CP relationship and requiring too much noseweight, you could always make them PIVOTING fins, which if done right have NO adverse affects on the CG/CP relationship and can minimize the amount of nose weight required.

Basically, only the area of the fin ahead of the pivot has to be accounted for in the stability calculations... IOW, if the pivot point is at the 1/4 chord line, only the part of the fins IN FRONT of the pivot "axle" point contributes to instability... for Rocksim/Open Rocket simulations, you basically add "fixed" fins the size and shape of the area of the fin AHEAD of the fin pivot point in the simulation, to determine what the aerodynamic effects on the CG/CP relationship are and thus amount of noseweight required...


Later! OL J R : )
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